Generally speaking, retractable landing gear should occupy minimum space when retraced into the fuselage, and naturally it should be as light as possible. Some kinds of aircraft, such as combat or fighter planes, require a structure or fuselage which is as streamlined as possible to reduce resistance to forward movement. Retractable undercarriages or landing gear have always been used to improve penetration through the air. Retractable landing gear is landing gear capable of taking two positions:
a first or "extended" position enabling the aircraft to land or take off; and
a second or "retracted" position for use in flight, in which the gear is retracted into housings provided for the purpose in the fuselage.
Consequently, when landing gear is provided for such aircraft, it must be designed in such a manner that, once retracted, it occupies the minimum possible space in order: firstly to be fully received in said housings; and secondly to leave sufficient space for all the other components that need to be housed in the fuselage, such as controls, electronics, an engine, and fuel tanks.
An essential characteristic of landing gear for such an aircraft is that when it is fully retracted, all its parts must be accurately folded and occupy minimum space, and further the wheel may take up a position relative to the leg which is not necessarily the same as the position which it occupies when the landing gear is in the extended position.
To obtain such results, various types of aircraft landing gear have been made mainly comprising: a strut having one end connected to the aircraft structure; a shock absorber cooperating with the other end of the strut; said shock absorber having running gear, such as pneumatic tyres mounted on hubs, at its end furthest from the strut; and a control actuator having one end connected to the structure and its other end connected to the strut, for example, in such a manner that depending on the two possible positions of the actuator, the strut is either in a landing gear extended position or else in a landing gear retracted position.
Such landing gear generally also includes a "collapsible" side brace having one end connected to the aircraft structure and having its other cooperating either with the strut or with the shock absorber. The collapsible side brace generally comprises two relatively rotatable levers and one of the levers drives a complicated crank system to pivot the wheel to enable it to take up two defined positions relative to the strut depending on whether the strut is in the landing gear extended position or in the landing gear retracted position.
The known landing gear outlined above gives good results, but it is undoubtedly complicated since it is made up of numerous components, and this means that it does not satisfy another characteristic expected of landing gear, namely lightness, or at least as low a weight as possible.
Preferred embodiments of te present invention mitigate these drawbacks and provide an aircraft landing gear in which the leg that carries the running gear is pivotable about the strut axis as the landing gear moves between an extended position and a retracted position inside the structure, and in which the landing gear requires few components, thus enabling it to be relatively light and also less expensive than prior art landing gear.